I think it's held throughout history, but then again, throughout history most of the world has had some sort of aristocracy.

The historical exception is the U.S. from 1945 to 1973, as well as perhaps a few other examples (maybe Scandinavia today, or the U.S. in the early/mid 1800s?). In that time period - really, no more than a generation - we saw a big leveling of income distribution, where people born to modest families suddenly had the creature comforts that a generation before had been reserved for the aristocracy. I think most people would agree that this is a generally desirable state for a society, so it might be worth asking what was different about those time periods that made them the historical exception?